HELP ME

I currently have an amp( I know how to power it) it is a car stereo amp. I m trying to hook up a car subwoofer to my receiver. I hooked the L+ and the R- to the subwoofer on the bridge and hooked the high input to the hifis on the reciever. But all that comes out is little bass and lyrics. I want the subwoofer strictly for bass so it gets a lot of power. any ideas?/
Brant

Kenwood A34 amplifier schematics:
Does anyone have technical service or other schematics for the Kenwood A34 stereo amplifier?

Need to find out what voltages are present on the flat 4 wire ribbon cables that connect this amplifier to the tuner, tape cassette deck, CD-player in the same series.

Any help appreciated!